Common easy open end closures for beer and beverage containers have a central or center panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “consumer side,” of the end closure. Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin sheet of aluminum or steel. End closures for such containers are also typically constructed from a cut-edge of thin sheet of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container.
The seaming process typically requires the container and the can end to be elevated and clamped between a base plate and a seaming chuck. A first set of seaming rollers are rotated about the seaming chuck along the open end of the container with sufficient pressure to form the first portion of a double joining seam. When the first step in forming the double seam has been completed, the first pair of opposed seaming rollers is retracted, and the seaming rollers of a second pair are actuated to complete the double seam. When the seaming of the can end to the can body is complete, the second set of seaming rollers is retracted, and the base plate piston is retracted. At the same time, a seamer knockout piston carried centrally of the seaming chuck is actuated to ensure freeing of the sealed container from the chuck to complete the seaming operation.
The can ends are generally provided with information on an upper or public side prior to seaming. The information is typically directed to recycling information and the like. The information is added to the end during the manufacture of the end by stamping or incising. The incising process leaves extra metal adjacent the lettering. A pressure within the can may also cause the center panel of the can end to flex or bow slightly upward. This may cause the incising to distort and/or flex upwardly as well. During seaming, the excess metal and/or the distorted incising may cause metal build up on the seamer knockout. Thinner gauge can ends also tend to pucker from the incising which may compound the build-up. As the excess material builds on the seamer knockout, it leaves a circumferential scratch on subsequent can ends as the rotating can ends are engaged by the stationary seamer knockout.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior tooling assemblies for seaming a can end to a can body of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.